The invention relates to an improved testing apparatus, and more particularly to an apparatus useful in evaluating the thermal stability of a thermal quenching oil (liquid hydrocarbon) under dynamic conditions. The invention also relates to a method of evaluating the thermal stability of a thermal quenching oil (liquid hydrocarbon) under dynamic conditions.
In the metalworking industries, it is common practice to use certain hydrocarbon liquids known as quenching oils for the purpose of quenching (i.e., controlled cooling) pieces of metal which have been heated to elevated temperatures to improve metallurgy. On the other hand, the repeated subjecting of the quenching oil to thermal shock (by the dipping thereinto of very hot pieces of metal) eventually causes degradation of the oil, with the formation of sludge, a marked increase in the viscosity of the oil, etc. It is important to the refiner and marketer of quenching oils to be able to quickly evaluate in the laboratory the thermal stability of the quenching oils he is offering for sale, so that he will know whether or not his products meet certain specifications.
An object of this invention is to provide a testing apparatus and method useful for dynamically evaluating the thermal stability of a liquid, and specifically of the quenching oil.
Another object is to provide testing apparatus of the aforementioned type and method which actually simulates the conditions involved in actual commercial use of a quenching oil, i.e., very hot metal immersed into a relatively large amount of oil having a temperature substantially lower than that of the hot metal.
Another object is to perform the testing in a relatively short period of time.
A further object is to provide a quenching oil testing apparatus which is simple in construction, easy to operate and repeatable.
A still further object is to provide a novel (laboratory) testing apparatus for quenching oils.
U.S. Pat. No. 3,680,356, issued Aug. 1, 1972 to George F. Felton, Jr., discloses a testing apparatus for use in evaluating the thermal stability of a quenching oil. However, to evaluate said stability by the disclosed apparatus requires weeks rather than days by the present invention. Furthermore the disclosed apparatus is subject to breakdown because of the relatively many moving parts. Also for safety reasons the temperature of the oil should not be allowed to exceed 300.degree.-400.degree.F because of the possibility of fire. This is a particular problem when the oil has a low flash point. The flash point of a typical conventional quench oil is about 320.degree.-400.degree.F.